# l1 = [1, 2, 3]
# l2 = [1, 2, 3]
# l3 = l2
# print(l1 == l2)
# print(l1 is l2)
# print(l2 is l3)
class Cache(object):

    def __init__(self):
        self.data = []

    def add(self, item):
        self.data.append(item)

    def remove(self, item):
        self.data.remove(item)

    def show(self):
        print(self.data)

    def __len__(self):
        return len(self.data)

#
cache = Cache()
cache.add("yuan")
cache.add("rain")
cache.add("alvin")
#
# # print(cache.data)
# cache.show()
# cache.remove("yuan")
# cache.show()
# data = []
# data.append("yuan")
# data.append("rain")
# data.append("alvin")
# data.remove("yuan")
print(len(cache))
